• Journal of Korean Society of Forest Science
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• v.66 no.1
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• pp.16-36
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• 1984

It is very important in forestry to study the shear strength of weathered granitic soil, because the soil covers 66% of our country, and because the majority of land slides have been occured in the soil. In general, the causes of land slide can be classified both the external and internal factors. The external factors are known as vegetations, geography and climate, but internal factors are known as engineering properties originated from parent rocks and weathering. Soil engineering properties are controlled by the skeleton structure, texture, consistency, cohesion, permeability, water content, mineral components, porosity and density etc. of soils. And the effects of these internal factors on sliding down summarize as resistance, shear strength, against silding of soil mass. Shear strength basically depends upon effective stress, kinds of soils, density (void ratio), water content, the structure and arrangement of soil particles, among the properties. But these elements of shear strength work not all alone, but together. The purpose of this thesis is to clarify the characteristics of shear strength and the related elements, such as water content ($w_o$), void ratio($e_o$), dry density (${\gamma}_d$) and specific gravity ($G_s$), and the interrelationship among related elements in order to decide the dominant element chiefly influencing on shear strength in natural/undisturbed state of weathered granitic soil, in addition to the characteristics of soil hardness of weathered granitic soil and root distribution of Pinus rigida Mill and Pinus rigida ${\times}$ taeda planted in erosion-controlled lands. For the characteristics of shear strength of weathered granitic soil and the related elements of shear strength, three sites were selected from Kwangju district. The outlines of sampling sites in the district were: average specific gravity, 2.63 ~ 2.79; average natural water content, 24.3 ~ 28.3%; average dry density, $1.31{\sim}1.43g/cm^3$, average void ratio, 0.93 ~ 1.001 ; cohesion, $ 0.2{\sim}0.75kg/cm^2$ ; angle of internal friction, $29^{\circ}{\sim}45^{\circ}$ ; soil texture, SL. The shear strength of the soil in different sites was measured by a direct shear apparatus (type B; shear box size, $62.5{\times}20mm$; ${\sigma}$, $1.434kg/cm^2$; speed, 1/100mm/min.). For the related element analyses, water content was moderated through a series of drainage experiments with 4 levels of drainage period, specific gravity was measured by KS F 308, analysis of particle size distribution, by KS F 2302 and soil samples were dried at $110{\pm}5^{\circ}C$ for more than 12 hours in dry oven. Soil hardness represents physical properties, such as particle size distribution, porosity, bulk density and water content of soil, and test of the hardness by soil hardness tester is the simplest approach and totally indicative method to grasp the mechanical properties of soil. It is important to understand the mechanical properties of soil as well as the chemical in order to realize the fundamental phenomena in the growth and the distribution of tree roots. The writer intended to study the correlation between the soil hardness and the distribution of tree roots of Pinus rigida Mill. planted in 1966 and Pinus rigida ${\times}$ taeda in 199 to 1960 in the denuded forest lands with and after several erosion control works. The soil texture of the sites investigated was SL originated from weathered granitic soil. The former is situated at Py$\ddot{o}$ngchangri, Ky$\ddot{o}$m-my$\ddot{o}$n, Kogs$\ddot{o}$ng-gun, Ch$\ddot{o}$llanam-do (3.63 ha; slope, $17^{\circ}{\sim}41^{\circ}$ soil depth, thin or medium; humidity, dry or optimum; height, 5.66/3.73 ~ 7.63 m; D.B.H., 9.7/8.00 ~ 12.00 cm) and the Latter at changun-long Kwangju-shi (3.50 ha; slope, $12^{\circ}{\sim}23^{\circ}$; soil depth, thin; humidity, dry; height, 10.47/7.3 ~ 12.79 m; D.B.H., 16.94/14.3 ~ 19.4 cm).The sampling areas were 24quadrats ($10m{\times}10m$) in the former area and 12 in the latter expanding from summit to foot. Each sampling trees for hardness test and investigation of root distribution were selected by purposive selection and soil profiles of these trees were made at the downward distance of 50 cm from the trees, at each quadrat. Soil layers of the profile were separated by the distance of 10 cm from the surface (layer I, II, ... ...). Soil hardness was measured with Yamanaka soil hardness tester and indicated as indicated soil hardness at the different soil layers. The distribution of tree root number per unit area in different soil depth was investigated, and the relationship between the soil hardness and the number of tree roots was discussed. The results obtained from the experiments are summarized as follows. 1. Analyses of simple relationship between shear strength and elements of shear strength, water content ($w_o$), void ratio ($e_o$), dry density (${\gamma}_d$) and specific gravity ($G_s$). 1) Negative correlation coefficients were recognized between shear strength and water content. and shear strength and void ratio. 2) Positive correlation coefficients were recognized between shear strength and dry density. 3) The correlation coefficients between shear strength and specific gravity were not significant. 2. Analyses of partial and multiple correlation coefficients between shear strength and the related elements: 1) From the analyses of the partial correlation coefficients among water content ($x_1$), void ratio ($x_2$), and dry density ($x_3$), the direct effect of the water content on shear strength was the highest, and effect on shear strength was in order of void ratio and dry density. Similar trend was recognized from the results of multiple correlation coefficient analyses. 2) Multiple linear regression equations derived from two independent variables, water content ($x_1$ and dry density ($x_2$) were found to be ineffective in estimating shear strength ($\hat{Y}$). However, the simple linear regression equations with an independent variable, water content (x) were highly efficient to estimate shear strength ($\hat{Y}$) with relatively high fitness. 3. A relationship between soil hardness and the distribution of root number: 1) The soil hardness increased proportionally to the soil depth. Negative correlation coefficients were recognized between indicated soil hardness and the number of tree roots in both plantations. 2) The majority of tree roots of Pinus rigida Mill and Pinus rigida ${\times}$ taeda planted in erosion-controlled lands distributed at 20 cm deep from the surface. 3) Simple linear regression equations were derived from indicated hardness (x) and the number of tree roots (Y) to estimate root numbers in both plantations.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.496-503
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• 2016

To analyze an infinite slope that is reinforced with stabilizing piles, the forces on the stabilizing pile were estimated by the theory of plastic deformation and the theory of plastic flow and the effects of diverse factors on the factor of safety of an infinite slope were investigated. According to the results of the analyses, the factor of the safety of the slope reinforced with stabilized piles were increased tremendously and the factor of safety decreased as the center to center distance of the stabilizing pile increased. The effect of the existence of seepage of the infinite slope with stabilizing piles on the factor of safety appears to be insignificant. Considering the formulated factor of safety of an infinite slope with stabilizing piles, the width and length of the element of the infinite slope and force on the stabilizing pile influence the factor of safety of the infinite slope with a stabilizing pile including the soil strength parameter, inclination of the slope and depth of the slope, which are important for calculating the factor of safety of a non-reinforced infinite slope. The factor of safety of an infinite slope with stabilizing piles derived from the theory of plastic deformation were increased significantly with the internal friction angle of the soil, and the minimum and the maximum factor of safety under the conditions considered in this study were 13.7 and 65.6, respectively. As the diameter of the stabilizing pile increased, the forces on the stabilizing pile also increased but the factor of safety of the infinite slope with stabilizing piles decreased due to the effects of the width and the length of the element of the infinite slope. The factor of safety of the infinite slope with stabilizing piles derived from plastic flow were much larger than that of the non-reinforced infinite slope and the factor safety of the infinite slope with a stabilizing pile increased with increasing product of the flow velocity and plastic viscosity ( ) and the factor of safety of the infinite slope with stabilizing piles decreased with increasing center to center distance of the pile.

• The Journal of Engineering Geology
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• v.26 no.3
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• pp.383-392
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• 2016

This study is to evaluate the physical and mechanical properties on the Ipseok-dae columnar joints of Mt. Mudeung National Park. For these purposes, physical and mechanical properties as well as discontinuity property on the Mudeungsan tuff, measurement of vibration and local meteorology around columnar joints, and ground deformation by self-weight of columnar joints were examined. For the physical and mechanical properties, average values were respectively 0.65% for porosity, 2.69 for specific gravity, 2.68 g/cm³ for density, and 2411 m/s for primary velocity, 323 MPa for uniaxial compressive strength, 81 GPa Young's modulus, and 0.25 for Poisson's ratio. For the joint shear test, average values were respectively 3.15 GPa/m for normal stiffness, 0.38 GPa/m for shear stiffness, 0.50 MPa for cohesion, and 35° for internal friction angle. The JRC standard and JRC chart was in the range of 4~6, and 1~1.5, respectively. The rebound value Q of silver schmidt hammer was 57 (≒ 90 MPa). It corresponds 20% of the uniaxial compressive strength of intact rock. The maximum vibration value around the Ipseok=dae columnar joints was in the range of 0.57 PPV (mm/s)~2.35 PPV (mm/s). The local meteorology of surface temperature, air temperature, humidity, and wind on and around columnar joints appeared to have been greatly influenced the weather on the day of measurement. For the numerical analysis of ground deformation due to its self-weight of the Ipseok-dae columnar joints, the maximum displacement of the right ground shows when the ground distance is approximately 2 m, while drastically decreased by 2~4 m, thereafter was insignificant. The maximum displacement of the middle ground shows when the ground distance is approximately 0~2 m, while drastically decreased by 3~10 m, thereafter was insignificant. The maximum displacement of the left ground shows when the ground distance is approximately 5~6 m, while drastically decreased by 6~10 m, thereafter was insignificant.

• Journal of Korean Society of Forest Science
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• v.89 no.2
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• pp.275-284
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• 2000

This study was carried out to analyze the mechanical properties of soil and the slope stability on the fill slope of forest road constructed in the regions which consist of igneous and metamorphic rock area. The results were summarized as follows. 1) Soil type by Unified Soil Classification System(USCS) was classified as SW in soil slope, GP in weathered rock slope, GP in soft rock slope for both types of parent rock, but gravelly soil slopes in igneous and metamorphic rock area were classified as SP and GW, respectively. 2) Dry unit weight was $1.34g/cm^2{\sim}1.59g/cm^2$, specific gravity 0.57~0.61, and void ratio 0.66~0.93 in the case of igneous rock area, a dry unit weight was $1.35g/cm^2{\sim}1.51g/cm^2$, specific gravity 2.67~2.77, and void ratio 0.78~1.01 in the case of metamorphic rock area. 3) The strength parameters such as internal friction angle(${\phi}$) and cohesion(c) were selected and tested for slope stability analysis. ${\phi}$ and c of soil in igneous rock area were within the range of $29.51^{\circ}{\sim}41.82^{\circ}$ and $0.03kg/cm^2{\sim}0.38kg/cm^2$, respectively, and $21.43^{\circ}{\sim}41.43^{\circ}$ and $0.05kg/cm^2{\sim}0.44kg/cm^2$ in metamorphic rock area, respectively. 4) Result of the slope stability analysis of forest road showed that, in the weathered rock slope of igneous rock and the weathered rock and soil slope of metamorphic rock area, the possibility of slope failure was high as safety factor was below 1.0.

• The Journal of Engineering Geology
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• v.24 no.1
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• pp.111-122
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• 2014

For accurate laboratory evaluations of soil deposits, it is essential that the samples are undisturbed. An artificial ground-freezing system is the one of the most effective methods for obtaining undisturbed samples from sand deposits. The objective of this study is to estimate the shear strengths and the characteristics of elastic waves of frozen-thawed and unfrozen specimens through the undrained triaxial compression test. For the experiments, Jumunjin standard sands are used to prepare frozen and unfrozen specimens with similar relative densities (60% and 80%). The water pluviation method is used to simulate the fully saturated condition under the groundwater table. When thawing the frozen specimens, the temperature is measured every minute. After the specimens are completely thawed, undrained triaxial compression tests are conducted using the same procedures as for the unfrozen specimens. During the triaxial tests (saturation, consolidation, and shear phase), compressional and shear waves are measured. The results show that the freeze-thaw process has minor effects on the peak deviatoric stress and shear strength values, and that the process does not affect the internal friction angle. The compressional wave velocity increases with increasing B-value to 1800 m/s in the saturation phase, but tends to remain constant in the process of consolidation and shearing. The shear wave velocity decreases with increasing B-value in the process of saturation, but changes velocity in accordance with the change in effective stress in the processes of consolidation and shearing. The compressional wave velocity has similar values regardless of the freeze-thaw process, but values of shear wave velocity are slighly lower in frozen-thawed specimens than in unfrozen specimens. This study is a preliminary experiment for estimating the shear strength and characteristics of elastic wave velocity in undisturbed frozen specimens that have been obtained using the artificial ground-freezing method.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.6
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• pp.306-318
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• 2018

In order to evaluate the seismic capacity of massive vertical type breakwaters which have intensively been deployed along the coast of South Korea over the last two decades, we carry out the preliminary numerical simulation against the PoHang, GyeongJu, Hachinohe 1, Hachinohe 2, Ofunato, and artificial seismic waves based on the measured time series of ground acceleration. Numerical result shows that significant sliding can be resulted in once non-negligible portion of seismic energy is shifted toward the longer period during its propagation process toward the ground surface in a form of shear wave. It is well known that during these propagation process, shear waves due to the seismic activity would be amplified, and non-negligible portion of seismic energy be shifted toward the longer period. Among these, the shift of seismic energy toward the longer period is induced by the viscosity and internal friction intrinsic in the soil. On the other hand, the amplification of shear waves can be attributed to the fact that the shear modulus is getting smaller toward the ground surface following the descending effective stress toward the ground surface. And the weakened intensity of soil as the number of attacking shear waves are accumulated can also contribute these phenomenon (Das, 1993). In this rationale, we constitute the numerical model using the model by Hardin and Drnevich (1972) for the weakened shear modulus as shear waves go on, and shear wave equation, in the numerical integration of which $Newmark-{\beta}$ method and Modified Newton-Raphson method are evoked to take nonlinear stress-strain relationship into account. It is shown that the numerical model proposed in this study could duplicate the well known features of seismic shear waves such as that a great deal of probability mass is shifted toward the larger amplitude and longer period when shear waves propagate toward the ground surface.

• Journal of radiological science and technology
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• v.32 no.3
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• pp.335-341
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• 2009

Purpose : The medical imaging issuance is changed from conventional film method to Digital Compact Disk solution because of development on IT technology. However other medical record department's are undergoing identification check through and through whereas medical imaging department cannot afford to do that. So, we examine present applicant's recognition of private intelligence safeguard, and medical imaging issuance condition by CD & DVD medium toward various medical facility and then perform comparative analysis associated with domestic and foreign law & recommendation, lastly suggest standard for medical imaging issuance and process relate with internal environment. Materials and methods : First, we surveyed issuance process & required documents when situation of medical image issuance in the metropolitan medical facility by wire telephone between 2008.6.1$\sim$2008.7.1. in accordance with the medical law Article 21$\sim$clause 2, suggested standard through applicant's required documents occasionally - (1) in the event of oneself $\rightarrow$ verifying identification, (2) in the event of family $\rightarrow$ verifying applicant identification & family relations document (health insurance card, attested copy, and so on), (3) third person or representative $\rightarrow$ verifying applicant identification & letter of attorney & certificate of one's seal impression. Second, also checked required documents of applicant in accordance with upper standard when situation of medical image issuance in Kyung-hee university medical center during 3 month 2008.5.1$\sim$2008.7.31. Third, developed a work process by triangular position of issuance procedure for situation when verifying required documents & management of unpreparedness. Result : Look all over the our manufactured output in the hospital - satisfy the all conditions $\rightarrow$ 4 place(12%), possibly request everyone $\rightarrow$ 4 place(12%), and apply in the clinic section $\rightarrow$ 9 place(27%) that does not medical imaging issuance office, so we don't know about required documents condition. and look into whether meet or not the applicant's required documents on upper 3month survey - satisfy the all conditions $\rightarrow$ 629 case(49%), prepare a one part $\rightarrow$ 416 case(33%), insufficiency of all document $\rightarrow$ 226case(18%). On the authority of upper research result, we are establishing the service model mapping for objective reception when image export situation through triangular position of issuance procedure and reduce of friction with patient and promote the patient convenience. Conclusion : The PACS is classified under medical machinery that mean indicates about higher importance of medical information therefore medical information administrator's who already received professional education & mind, are performer about issuance process only and also have to provide under ID checking process exhaustively.